Autism is lifelong. Autism is not an illness or disease so cannot be cured. Autism is a developmental disability that impacts how people perceive the world, and communicate with others.
The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) 2013 describes autism as:
Persistent difficulties with social communication and social interaction’ and ‘restricted and repetitive patterns of behaviours, activities or interests’ (this includes sensory behaviour), present since early childhood, to the extent that these ‘limit and impair everyday functioning’.